The present invention relates generally to confocal microscopy, and more particularly to a confocal microscope which incorporates piezoelectric bimorph cells to scan an objective image plane.
The principle of confocal microscopy was first taught by M. Minsky in the mid 1950s, and is described in Minsky's U.S. Pat. No. 3,013,467. In this well known technique, light from a point source is used to illuminate a very small region of a sample object, and a point detector is used to detect light reflected from that small area. By limiting the spatial dimension of the detector, images with resolution better than the classical diffraction limit may be obtained. An image of the sample object is formed one point at a time by synchronously scanning the light source and the detector, much in the same way that a scanned television image is formed one pixel at a time.
Confocal microscopy has many advantages over standard optical microscopy. For example, confocal microscopy allows for optical sectioning (i.e., depth discrimination) of translucent specimens, and provides excellent images of the surface topology of reflective opaque specimens. In addition, a confocal microscope has a horizontal resolution up to 1.4 times that of a conventional microscope, and can screen out fogginess normally observed with standard microscopes used on living specimens.
In a more specific technique known as Scanning Confocal Fluorescence Laser Microscopy (SCFLM), the illuminating beam is used to stimulate fluorescence in a sample object. The light emitted by the fluorescing sample is detected and used to form an image in the same manner as described above. SCFLM is especially useful in generating three-dimensional images of biological specimens.
There have been several scanning techniques and systems used in confocal microscope imaging. One such technique is to mechanically raster a specimen relative to the light source. This technique allows a very simple optical system to be used, and also gives space-invariant imaging. Space-invariant imaging ensures that resolution and contrast are identical across the entire field of view, and are completely decoupled from magnification. However, this technique results in relatively slow image acquisition, typically on the order of a few seconds. Also, this technique is not practical in situations where the specimen cannot be moved in a tightly controlled manner.
Previous techniques for scanning a light beam relative to a stationary sample include the use of vibrating galvanometer-type mirrors or rotating mirror wheels. In addition, an acousto-optic beam deflector technique has been described by S. Goldstein in "A No-Moving-Parts Video Rate Laser Beam Scanning Type 2 Confocal Reflected-Transmission Microscope," J. Microsc., 153, RP1-RP2. The use of the latter two alternatives gives the possibility of television rate scanning, whereas vibrating mirror systems are usually relatively slow. The drawbacks to these techniques lie in the increased complexity of the optical system, the added expense, and the non-space-invariant imaging.
Yet another scanning technique is described by D. K. Hamilton and T. Wilson in "Scanning Optical Microscopy by Objective Lens Scanning," J. Phys. E., 19, 52-54 (1986). In this technique, the objective lens is itself scanned relative to a stationary optical system and a stationary object.
While each of the above described scanning techniques is useful in certain circumstances, each of these techniques has serious drawbacks in that they are expensive, relatively fragile, and not suitable for use outside of a laboratory setting.